these guys did a lot of damage but for me here the story of course we don't say oh those irresponsible siano bacteria. how could they? what were they thinking? because bacteria don't think. they're just bacteria. at the same time we are cso of behaving in a way that is perhaps analogous and those of us that are paying attention feel a great sense of responsibility about this and concern. what is the difference? in an effort to probe that question a bit i looked at all the catastrophes that could befall planets and i've decided perhaps they fit into four categories for kinds of planetary change categorized with respect to the influence of life. what i call planetary changes are just the random things that happen, when bad things happen to good planets. a big first balkin-ism causes mass extinction. these are catastrophes where life had nothing to do with it. it was just in the wrong place at the right time and all planets in the universe to some degree will have this kind of catastrophe. they second biological catastrophe. i gave an example of the cyanobacteria, this is when some species or g